The present technology generally relates to track systems and traction assemblies with tensioning devices that are used as wheel replacement for typically wheeled vehicles such as, but not limited to, farming and agricultural vehicles (e.g., tractors, harvesters, etc.) and construction and industrial vehicles (e.g., excavators, combines, forestry equipment, etc.) and power sports vehicles (e.g., ATV's, UTV's, etc.).
Several normally wheeled vehicles and particularly heavy wheeled vehicles (e.g., farming tractors, front loaders, harvesters, etc.) often have their wheels replaced by track systems that use an endless traction band (also called endless tracks) instead of a tire for propulsion or for steering. Vehicles equipped with track systems typically have improved floatation and traction, particularly when operated over soft terrains.
Endless tracks have been used on such vehicles to increase surface area in contact with the ground. This increased footprint results in a lower force per unit area on the ground being traversed than that of the same vehicle having conventional wheels (and being of the same weight).
In a typical conventional an endless track system, an endless track is driven by a sprocket in which teeth of the sprocket engage links of the track to drive the track, and thus the vehicle, forward. Support wheels are typically conventionally attached to the vehicle through independent suspensions and roll over the track, which is in contact with the ground. In such cases, the support wheels typically do not drive the vehicle forward, as only the sprocket is used for providing movement. The direct engagement of the sprocket does not allow for track slippage relative to the sprocket and/or due to friction between track and sprocket.
During operation, some components of such conventional track systems, particularly the idler wheels and support wheels, can experience uneven load distributions, especially upon braking. Braking events generally prompt an upward movement of the idler wheel which affect the tension of the endless track. This is particularly true for the idler wheels located towards the front of the track system. As upward movement of the idler wheels is generally desired when encountering varying obstacle, terrain variation and/or debris ingestion, conventional tracked vehicles are typically equipped with one or more tensioner systems adapted to substantially maintain the track at a predetermined tension in operation over various terrain profiles. Such tensioner systems aim at avoiding having the track slide off (disengage) the sprocket and/or the idler wheels during a sudden maneuver or a turn. Typically, such tensioner systems may also prevent excessive loads from being applied to the endless track, to the vehicle drive wheel, and to the vehicle suspension.
Additionally, track tension may impact power efficiency. In some situations, an over-tensioned or under-tensioned track may lead to power loss from excess friction and may accelerate wearing of the track system. However, radially upward movement of the idler wheels upon braking must be restrained as tension of the track is decreased (loosening the endless track leading to ratcheting of the track). As such, decreased tension in the endless track upon braking hinders the proper functioning of the track system and decreases the braking efficiency of the track system. Furthermore, upward movement of the idler wheels upon braking increases wearing of the track system, in part due to ratcheting but also due to the overall deformation of the track system. As such, the tensioner system in the track system aims at maintaining the perimeter defined by the wheels generally equal or superior to the nominal perimeter of the track.
Track tension is typically controlled by moving a sprocket or idler wheel that engages the track. A conventional passive mechanism for moving the sprocket or idler wheel is a track tensioner employing a grease-filled cylinder or an oil filled cylinder using an accumulator acting as a spring, which is referred to as a dynamic tensioner. A piston in the cylinder moves as grease is added or removed through a fitting. By its motion, the piston moves the sprocket or idler wheel relative to the track thereby causing the sprocket or idler wheel to either extend into the track path and increase the tension of the track or to withdraw from the path of the track and decrease the tension of the track.
Indeed, in track systems, the resultant force from track tension and track friction can induce a torque around the idler frame pivot, resulting in the rotation of the idler frame thereabout. This rotation then generally causes the idler wheel located at one end of the idler frame to move circularly about the radius of the idler frame pivot point, while causing the road wheels located at the other end of the tandem frame to move in the opposite direction circularly about the radius of the idler frame pivot point. This results in an increased load on the wheels, which are urged against the ground. The rotation of the idler frame can also cause the trailing portion of the track system to rise. This uneven load distribution can reduce the efficiency of the track system and even lead to premature failure thereof.
Moreover, some safety regulations in countries require that agricultural tracked vehicles be able to immobilize themselves from a given speed within a certain distance and/or meet a deceleration value. Those requirements are such that current mechanisms are inefficient if not deficient at avoiding the ratcheting phenomenon as described above.
Hence, there is a need for an improved track system having a dynamic or active track tensioning system that may mitigate at least some shortcomings of prior art track systems.
The required tensioning system should be able to allow rotational movement of the front wheel when the vehicle is in normal operation mode and be able to block, or limit, such movement in a braking event to avoid or at least limit the ratcheting of the sprocket wheel or drive wheel.
Rear suspensions for mountain bikes face similar issues as their suspension tends to compress when the user pedals, and such compression reduces the efficiency of the biker's pedaling. Solutions have been developed to adjust the damping of the suspension in relation with to the shock force applied on the suspension. An example of such a solution may be found in U.S. Pat. No. 8,770,360 in which an inertial valve is used to modulate the damping of the suspension element. However, such solution provides a means for maintaining the suspension blocked during operation and for unlocking the suspension element when an obstacle is hit. Furthermore, such solutions are configured to absorb a limited shock or force.